(PowerBuilder) About RSA Public/Private Keys

This example provides some additional information for understanding public/private key pairs. In demonstrates how a private key is a superset of the public key. A public key contains the modulus and exponent. The matching private key also contains the modulus and exponent, but also contains the additional private key parts.

Note: This example requires Chilkat v11.0.0 or greater.

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integer li_rc
integer li_Success
oleobject loo_Cert
oleobject loo_PubKey
oleobject loo_PrivKey

li_Success = 0

loo_Cert = create oleobject
li_rc = loo_Cert.ConnectToNewObject("Chilkat.Cert")
if li_rc < 0 then
    destroy loo_Cert
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// Load a digital certificate.
li_Success = loo_Cert.LoadFromFile("digitalCert.cer")
if li_Success = 0 then
    Write-Debug loo_Cert.LastErrorText
    destroy loo_Cert
    return
end if

// A .cer file does not contain the private key.  It should contain
// the public key...
loo_PubKey = create oleobject
li_rc = loo_PubKey.ConnectToNewObject("Chilkat.PublicKey")

loo_Cert.GetPublicKey(loo_PubKey)

// Let's have a look at it (in XML format).
Write-Debug "Public Key from Certificate:"
Write-Debug loo_PubKey.GetXml()

// An RSA public key consists of a modulus and exponent.

// An RSA private key includes both the modulus and exponent,
// as well as other "big" numbers: P, Q, D, etc.

// Let's load an RSA private key from a DER-encoded file:
loo_PrivKey = create oleobject
li_rc = loo_PrivKey.ConnectToNewObject("Chilkat.PrivateKey")

li_Success = loo_PrivKey.LoadAnyFormatFile("PrivateKey.key","")
if li_Success <> 1 then
    Write-Debug loo_PrivKey.LastErrorText
    destroy loo_Cert
    destroy loo_PubKey
    destroy loo_PrivKey
    return
end if

// If this private key is the matching half to the public key from
// the certificate, then the modulus and exponent should
// be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
Write-Debug "Private Key from DER:"
Write-Debug loo_PrivKey.GetXml()


destroy loo_Cert
destroy loo_PubKey
destroy loo_PrivKey